The pensioner who led the gang behind the £14m Hatton Garden heist was a former top lieutenant of crime boss Kenneth Noye and used his decades of criminal experience to mastermind the biggest burglary in English history.

Brian Reader’s closeness to top criminals can be revealed, following the convictions of three of his associates on Thursday for their involvement in the audacious theft, that left some of its 39 victims who lost their property devastated.

Reader, 76, had last year admitted his guilt for the heist that took place over the Easter weekend last year, when a group of men drilled through a 50cm-thick concrete wall and broke into 73 security boxes in London’s diamond district without leaving a forensic trace.

Hatton Garden heist: how swan song of old-school working-class criminal came together

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Reader was previously one of Noye’s “trusted” aides. Three decades ago both had been cleared of murdering a police officer.

The three further convictions on Thursday mean a total of nine people have now either pleaded guilty or been convicted in connection with the burglary at Hatton Garden, and handling of its mammoth haul of bullion, jewels and cash.

But the investigation and court procedings may be far from over against the gang who police say wanted the huge haul as their “pension pot”.

Police and prosecutors are expected to press the guilty for over £9m of the loot that is still missing and also for a key gang member who has never been caught, nicknamed Basil, caught on camera sporting a wig of red hair.

Those found guilty by a Woolwich crown court jury on Thursday were Carl Wood of Cheshunt, Hertfordshire; William Lincoln, 60, of Bethnal Green, east London and Hugh Doyle, 48, of Enfield, north London. A fourth man, Jon Harbinson, 42, of Benfleet, Essex, was acquitted.

Reader, of Dartford, Kent, had previously pleaded guilty to conspiracy to burgle with intent to steal jewellery. Three other main players had also pleaded guilty: John Collins, 75, of Islington, north London; Daniel Jones, 60, of Enfield, north London; and Terry Perkins, 67, also of Enfield.

The audacious heist and the fact three of the gang were pensioners captured the public’s imagination. Former Scotland Yard commander Peter Spindler, who oversaw the investigation told the Guardian: “It’s probably the last of its type.”

Spindler added that the gang made a string of errors that meant it took police a fortnight to start identifying them as prime suspects. He added: “They probably thought they had got away with it, and became complacent or arrogant.

“They were analogue criminals ill-prepared for digital detectives. That’s how they got caught.”

The gang were caught on audio bugs discussing the thrill of the heist, photographed as they met afterwards to discuss hiding the loot over pints in pubs and meals. Their movements were retrospectively tracked by high tech systems that could read their cars’ number plates and their constant ringing of each other, before and after the heist on mobile phones, proved their guilt.

Spindler, recently retired, added: “They are men of their time, one of the reasons they have not been successful, a decade or two ago, there was not the ANPR [automatic number plate recognition] or CCTV coverage there is now, and they would have had a better chance of getting away with it.”

Reader, lauded as the “guvnor” by the others in the Hatton Garden heist – in part because of his status in the criminal world – had previously been jailed for a total of nine years for conspiracy to handle stolen goods and dishonestly handling cash, after the £26m robbery at the Brink’s-Mat warehouse, near Heathrow airport.

Left to right: Carl Wood, William Lincoln, Jon Harbinson and Hugh Doyle in a sketch at Woolwich crown court. Photograph: Elizabeth Cook/PA

Reader, Perkins and Jones first entered the vault, while Wood joined them. Collins was said to be a lookout, while Lincoln allegedly acted as a getaway driver. Gas engineer Doyle later helped oversee an exchange of the loot at his workshop.

Detective superintendent Craig Turner, head of the Flying Squad that saved Scotland Yard’s blushes by cracking the case after police ignored an alarm triggered by the gang, rubbished the idea the gang were cuddly pensioners: “They are callous career criminals.”

Police said one victim had worked for 47 years and lost two-thirds of his savings to the gang. He had retired just five weeks earlier and so far just one-third of the money he saved up over five decades had been recovered.

Turner said of the gang: “It was their last hurrah, their pension pot.”

The four ringleaders who pleaded guilty to plotting the burglary – Reader, Perkins, Jones and Collins – face a maximum sentence of just under seven years.

But their friends and associates now fear fresh legal action could be brought against the men to recover more than £9m of the haul the police say is still missing, which could lead to extra jail time and the older men perishing in prison.

Those convicted may now face confiscation hearings which could see their assets such as houses and cars seized, and sentences increased by seven years for every £500,000 to £1m they are found to be withholding.

Reader’s full history could not be revealed until the trial against the four men ended. Both he and Noye were charged with murdering a police surveillance officer in the grounds of Noye’s home in January 1985. PC John Fordham was stabbed in the front and back as he kept watch on Noye – who was acquitted after claiming he acted in self defence.

Noye is currently in prison for an unrelated knife murder and was an alleged criminal mastermind of significant interest to police since the 1970s. He was alleged to have have bribed officers and was a police informant, as well as a mason. Police do not believe Noye was involved in the Hatton Garden heist.

The senior detective who investigated Brink’s-Mat, Brian Boyce, told the Guardian that “Reader was trusted by Noye” and was also close to other major crime figures such as the London-based Adams crime family.

When Reader’s home was raided by police they found a book on the diamond underworld, a diamond tester, a diamond gauge, diamond magazines. Also recovered during raids as police arrested the suspects was a book called Forensics for Dummies.

The gang had to clamber down a lift shaft to access a vault, where they disabled the alarm and other electrics. They then cut through a sliding iron gate and drilled three adjoining circular holes in the wall of the main vault with a Hilti DD350 diamond-tipped drill.

The hole drilled by the burglars that allowed them to gain access to the Hatton Garden Safe Deposit vault. Photograph: Metropolitan Police/PA

A hole 50cm deep, 25cm high and 45cm wide was cut 89cm off the ground to enter the vault, with Jones, a marathon runner, and Basil clambering through. But the gang only opened a fraction of the boxes inside, 73, of which 40 had valuables.

The burglary was up to three years in the planning and gang members scoured the area beforehand, and even visited the vault. They posed as gas repairmen as they got into the building that housed the safety box vault via a fire escape, after Basil let them into the main building.

Footage from inside the Hatton Garden safety deposit vault filmed by police who arrived on the scene.

Ringleaders used YouTube to watch demonstrations of how to use a drill powerful enough to punch through the thick reinforced concrete wall protecting the vault, and used the internet to research the equipment they might need.

Carl Wood, 58, of Cheshunt, Hertfordshire and William Lincoln, 60, of Bethnal Green, east London, were found guilty of conspiracy to burgle by the trial jury. Jon Harbinson, 42, of Benfleet, Essex, was aquitted of this charge.

Wood and Lincoln were also found guilty of conspiracy to conceal, convert or transfer criminal property. Harbinson and a fourth man – Hugh Doyle, 48, of Enfield, north London – were cleared of this charge.

Doyle, however, was found guilty of an alternative count of concealing, converting or transferring criminal property between 1 April and 19 May 2015.

Outside the courtroom, Doyle, who has been released on bail before sentencing, said he was disappointed by the verdict and would be looking at the possibility of appealing his conviction. “It’s highly likely we will be appealing the conviction,” he said. “I’m disappointed but would like to thank all those who have supported me throughout this – my friends and family.”